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Urban flooding has become an increasingly frequent and fatal natural hazard and numerical modeling techniques play a vital role in its prediction and management. We review urban flood numerical simulations by systematically summarizing the calculation methods of surface runoff, drainage systems, and coupled models. Following the review, accuracy and computational efficiency are found to be the two key areas hindering the quality improvement of urban flood models, so an investigation of the key trends in the improvement of model accuracy and computational efficiency is conducted. It is found that the 1D-2D coupling model, finite volume method, unstructured meshing method, and hybrid parallel computing applications are the most effective strategies. Furthermore, the complex coupling of models and the lack of validation data are still crucial challenges in the development of urban flood modeling. This result can be used as a guideline for hydrologists in choosing the proper method of urban flood numerical simulation according to the task. • The methods and applicability of urban flood numerical simulation are summarized to provide support for related research. • We propose that the urban flood model can be improved in two aspects: accuracy and calculation speed model. • The future development of urban flood numerical simulation tends to be modular with a complex coupling model. [ABSTRACT FROM AUTHOR]

• A non-destructive measurement method of surface roughness using frequency-domain interferometry with Hanning window energy center method was proposed for accurately measure the surface roughness of precision parts. • The theoretical measurement accuracy of the system reaches 5 nm. • To verify the accuracy of the system, an atomic force microscope was used for comparison and verification. The difference between the two measurement results was 12 nm. • This work provides a faster and more accurate non-destructive measurement method for surface roughness measurement. To accurately measure the surface roughness of precision parts, this paper proposes a non-destructive measurement method of surface roughness using frequency-domain interferometry as the core detection principle and the Hanning window energy center method as the signal demodulation method. The corresponding relationship between the height changes of the sample surface profile and the frequency density changes in the interference signal was established, and the Hanning window energy center method was used to accurately extract the periodic frequency, which can more accurately measure the surface roughness of the sample. After the spectrum correction method, the peak signal-to-noise ratio of the system reaches 50∼60 dB. When the signal-to-noise ratio is 54.8, the theoretical measurement accuracy of the system reaches 5 nm. The vibration error generated during the actual measurement process is only 20 nm. The measurement results of the roughness measuring instrument were compared and analyzed. The experimental results showed that this system has higher measurement accuracy and accuracy, and the maximum repeatability error is 7 nm. To further verify the accuracy of the system, an atomic force microscope was used for comparison and verification. The difference between the two measurement results was 12 nm. This work provides a faster and more accurate non-destructive measurement method for surface roughness measurement. [ABSTRACT FROM AUTHOR]

• A calculation method based on Paserval's theorem was proposed to establishes the accuracy theory of Hanning-window energy centrobaric method (HnWECM). • The results demonstrate that the variance of the estimated frequency using HnWECM is only proportional to the signal-to-noise ratio (SNR) and very close to the Cramér-Rao Lower Bound (CRLB). • The work reveals the reason of chosen HnWECM as the signal processing method of OCV technology and gives its accuracy theory, which will greatly promote the application of OCV technology. The Optical Coherence Velocimeter (OCV) technology is a technique for high-precision displacement and vibration measurement based on the principle of spectral domain optical coherence method. The key of this technology is to realize nanometer or even sub-nanometer measurement by high precision frequency estimation method called as Hanning-window energy centrobaric method (HnWECM). This paper analyses the error transmission process of HnWECM, and proposes a calculation method based on Paserval's theorem to establishes the accuracy theory of HnWECM. It shows that the variance of the estimated frequency using HnWECM is only proportional to the signal-to-noise ratio (SNR) and very close to the Cramér-Rao Lower Bound (CRLB). The estimation performance of HnWECM is verified and compared with other frequency estimation methods by simulation and experimental results. Both the theoretical analysis and simulation results show that the HnWECM has good statistical efficiency and the best anti-noise stability. This paper reveals the reason of chosen HnWECM as the signal processing method of OCV technology and gives its accuracy theory, which will greatly promote the application of OCV technology. [ABSTRACT FROM AUTHOR]

• A FR-FDOCT was proposed based on Mach–Zehnder interferometer with a tilted mirror which could generate simultaneously a series of accurate phase-delay interference signal. • FR-FDOCT is capable of acquiring artifact-free images by construction of both amplitude and phase of interferogram from multiple sets of phase-delay signals. • The Mach–Zehnder interferometric structure with a tilted mirror in reference arm could actively promote the innovation and development of OCT technology. We proposed a full-range Fourier-domain optical coherence tomography (FR-FDOCT) based on a Mach–Zehnder interferometer with a tilted mirror which could generate a series of accurate phase-delay interference signals simultaneously. The FR-FDOCT is capable of acquiring artifact-free images by the construction of both amplitude and phase of the interferogram from multiple sets of phase-delay signals. The Mach–Zehnder interferometer make the reference arm became single-way optical path which is more convenient to adjust the reference beam than the return-way optical path (which means the incident and reflected beams use the same optical path) of traditional systems. A series of phase-delay interference signals were simultaneously acquired by a home-made two-dimensional spectrometer when tilting the mirror in the reference arm. The technique was employed to measure an anterior chamber of a porcine eye with a high symmetric artifact suppression of more than 45 dB. The technology could achieve double-range images effectively without any additional scanning device. It could actively promote the innovation and development of OCT technology. [ABSTRACT FROM AUTHOR]